RESEARCH AND TRAINING IN THE TRAVIS LAB AT FSU
My principal research interests fall in the general area of ecological
genetics, the study of how selection molds the phenotypic and genetic variation
within and among natural populations. To
be specific, I am interested in why animal populations differ from one another
in body size, life history, and sexual behavior patterns.
When I find such differences, I ask whether they are genetically based
and, if so, whether they are maintained by different directions of natural and
sexual selection. Some of the
projects that I've undertaken within these general questions include asking why
least killifish (Heterandria formosa)
population densities vary over two orders of magnitude and why sailfin molly (Poecilia
formosa) males exhibit so much variation in body size
and growth patterns.
type of work makes a contribution in two broader areas.
First, it helps us understand the power and precision of evolutionary
adaptation by uncovering such adaptation on very
local scales. Second, it opens up
an important window on comparative ecology by helping us understand
cope with different ecological challenges in different locations.
The principles derived
from this type of work can be applied to a variety of situations, from
understanding how fishery stocks respond evolutionarily to harvesting to
understanding the subtle but important differences among ecological communities
that might appear superficially similar.
In order to ask these kinds of questions, my work must be grounded firmly
in both population genetics and ecology. After
all, if one wants to understand why selection pressures diverge between two
populations, one needs to be able to understand the comparative ecology of those
two populations; to understand the potential evolutionary ramifications of
ecological differences, one has to understand population genetic principles and
be able to apply them. As a result,
the work that my students and I have done has ranged from the purely population
genetical (e.g. Baer, 1998, Evolution 52:183-193)
to the purely ecological (e.g. McManus and Travis, 1998, Oecologia
I employ a variety of approaches to answer the questions that I ask. The "stock and trade" of the ecological geneticist is the combination of field observation and manipulative experiment. The work in my laboratory embraces this paradigm (see Coleman and Travis, 1998, Env. Biol. Fishes 51:87-96, and Baer and Travis, 2000, Evolution 54:238-244) even if sometimes the field observations and manipulative experiments are reported in separate papers (e.g. Leips and Travis, 1999, J. Anim. Ecol. 68:595ff and Leips et al., 2000, Ecological Monographs 70:289ff). More generally, my students and I try to use whichever method and approach seem most suited for the problem at hand, from mathematical modeling (e.g. Trexler and Travis, 2000, Bull. Marine Science 66:853-873) to classic breeding designs (e.g. McCune et al., 2002, Science 296:2398-2401). The best discussion of how I approach my work can be found in the book chapter that I wrote with David Reznick for a volume entitled Experimental Ecology (1998, editors William J. Resitarits, Jr. and Joseph Bernardo, Oxford University Press, see pages 310-352).
Continuing Projects in the Laboratory
The major project for me is the continuing study of the numerical dynamics and life history expression in populations of the least killifish, Heterandria formosa (Poeciliidae). Local populations vary dramatically in their numerical dynamics as well as their distributions of life history traits, from the size of offspring at birth to the sex ratios that are characteristic of each population. The patterns of this variation match the expectations derived from the theory of density-dependent selection. But whether divergent density-dependent selection pressures maintain the genetic distinctions among these populations remains to be proven.
The present work involves several observational components. I am conducting long-term, monthly surveys of two populations to discern the relative strength of intrinsic and extrinsic factors in their numerical dynamics; I am also measuring a variety of life-history traits with each survey. In addition, I am making biannual surveys of density and life-history trait expression in 14 additional populations and attempting to understand age structure in 6 populations via analysis of otolith rings (in collaboration with my former student Bob Allman, now at the National Marine Fisheries Service Lab in Panama City).
major experimental component is a large selection experiment on the effects of
density-dependent selection on mixed genetic stocks in artificial ponds.
Additional experimental work is examining the effects of the different
predators found in different populations and whether the observed differences
among populations in adult sex ratio has a foundation in distinct, genetically
controlled differences at birth.
are some older publications that provide an introduction to the basic ecology of
the least killifish (e.g. Travis et al., 1987, Ecology
68:611ff); the background for the present work can be found in Leips and Travis
1999 (J. Anim. Ecology 68:595ff) and
Leips et al. 2000 (Ecological Monographs
70:289ff). The most recent paper
from this project, Soucy and Travis 2003 (J. Evol. Biol. in press - watch
for it), describes how populations with historically higher densities exhibit
higher levels of genetic heterozygosity but only slightly higher levels of
multiple paternity. This paper
contains a very surprising result, which is that the multiple paternity rates in
H. formosa are extremely
low, in fact, the lowest rates reported for any poecilid fish.
The surprising aspect of this result is that there is no courtship in
this species and the mating system appears to be based on forced insemination
attempts by males and a generally low level of female cooperation.
Many scientists (at least the ones with which Iíve spoken about this
problem) expected that we would find high rates of multiple paternity.
I continue to work on problems associated with the variation in life history and sexual behavior within and among populations of the sailfin molly, Poecilia latipinna. I am preparing manuscripts that describe the results of two long-term studies. One of these studies, done in collaboration with Joel Trexler, was on the hierarchical distribution of variation among and within populations across the eastern half of the geographic range of the species. The other study, done with Margaret Ptacek, Carliane Johnson, Neva Martin, and Tom Waltzek, was a detailed analysis of the quantitative genetic variation involved with differences and life history and sexual behavior between a population from Florida and a population from South Carolina. A general, although dated, summary of the work of my colleagues and I on the sailfin molly can be found toward the back of the chapter I wrote with David Reznick in the book entitled Adaptation, published in 1996 by Academic Press and edited by Michael Rose and George Lauder. Some of the horizons of the behavioral work on the mollies are described in two papers written with former postdoctoral scholar Margaret Ptacek (Ptacek and Travis, 1996, Animal Behaviour 52:59ff and Ptacek and Travis, 1997, Evolution 51:1217ff.
††††††††††† I retain an interest in the population ecology and genetics of the frogs that breed in temporary ponds. This was the major focus of my research for many years and from time to time my students, postdoctoral colleagues and I return to this system. Most recently, my students and I have studied how tadpoles determine the timing of metamorphosis and whether a species that breeds in permanent ponds, Hyla cinerea, adjusts its timing in ways that are fundamentally different than from its sister species, Hyla gratiosa, which breeds in temporary ponds (Leips et al., 2000, Ecology 81:2997-3008). In earlier work, we asked whether the outcome of interspecific competition would be affected by variation in water chemistry (Warner et al., 1993, Ecology 74:183-194) and whether the offspring of adult males that acquired mates would have higher fitness in the larval and juvenile stages than half-sibs sired by males that did not acquire mates (Woodward et al., 1988, Evolution 42:784-794).
Graduate Student Training in the Travis Lab
††††††††††† The goal of my training is to help each student become an independent scientist with a cohesive view of the discipline, the capacity to develop a successful program of research, and the skill to convey ideas and concepts to peers and students alike. I try to accomplish this with the extensive help of my colleagues at FSU through a program of graduate course work, independent study, lab meetings, journal clubs, and research. We try to tailor the mixture of those elements to the needs and interests of each student.
The common ground among my diverse students is found in their passion for evolutionary biology and ecology, their rather hard-nosed empirical orientation, their appreciation and understanding of theory, and their dedication to their work. I encourage (some might say "demand") my students to read broadly and papers on any topic are fair game for our weekly discussions. While all of my students have taken substantial training in statistics and/or mathematics, each acquired specific technical skills that were important for his or her research.
My graduate students have developed their own dissertation projects, some of which have been directly connected with one of the "main" lab projects while others have not. My responsibility is to guide each student into a research project that is well-matched to his or her interest, addresses an important conceptual problem of general interest, and is likely to yield interesting results (regardless of how individual experiments turn out). In other words, my job is to help insure that each project is likely to capture the attention of other scientists and produce results that can be published in very good journals. This requires that my students work in conceptual areas in which I am knowledgeable and on systems with which I am familiar. My students have worked with considerable latitude within those boundaries, executing successful dissertations on subjects from the quantitative genetics of morphological characters in frogs to the physiological ecology of resource allocation in mollies to the community ecology of Amazonian rainforest frogs.
††††††††††† I have been fortunate in the excellent graduate students who have studied in my laboratory, from whom I've learned a great deal. They include:
Michael F. Antolin, now at Colorado State University
Charles F. Baer, now at Indiana University
Michael S. Blouin, now at Oregon State
Felicia C. Coleman, now at Florida State
Sharon Forster-Blouin, now a veterinarian in
Rebecca C. Fuller, now at Florida State
Claude Gascon, now at Conservation
International in Washington, DC
Lisa Horth, now at the University of
Jeffrey Leips, now at University of
Michael McManus, now at the Missouri
Department of Conservation
Mark W. Schwartz, now at University of
Joel C. Trexler, now at Florida International University
The material cited in the previous paragraphs offers an introduction to
my work. But equally important are
the papers and essays from my laboratory that have been written by my students
and postdoctoral associates. Some
of these are derived from dissertation research but others reflect "side
projects" of one sort or other. These
papers offer a glimpse at the variety of work conducted in the lab and the
diversity of issues that all of us find interesting.
Here is a sample of recent student papers that reflects that variety and
C. F. 1999.
Among-locus variation in FST: fish, allozymes, and the
Lewontin-Krakauer test revisited.
R. C. 2002.
Lighting environment predicts relative abundance of male color morphs in
bluefin killifish populations. Proc. R. Soc.
Lond. B 269:1457-1465.
R. A., and C. B. Grimes. 2002.
Temporal and spatial dynamics of spawning,
settlement, and growth of gray snapper (Lutjanus
griseus) from the West Florida shelf as
from otolith microstructure. Fishery
Melanic body-color and aggressive mating-behavior are correlated traits
mosquitofish (Gambusia holbrooki).
Proc. Roy. Soc. Lond. B 270:1033-1040.
M. S. 2003.
Evaluation of the hatching trigger and larval ecology of the
salamander Amphiuma means.
Herpetologica (in press).